To satisfy my curiosity and to provide further info for anyone viewing list archives, I benchmarked assigning a new table() vs. running clear_table() on tables of various sizes & complexities. Assigning a new table() was clearly the winner by a huge margin.
It should be noted that these two methods are not completely equivalent. I run a script where a current table is periodically moved to an old table, and the current table cleared for further use. So, with A & B being tables of the same type:
B = A;
A = table();
works as intended, as B now contains the prior contents of A, and A is a new empty table.
B = A;
clears both, as they both point to the same table.